Thought I'd continue this topic over here. Another way to tell if you have a 4ZD1/2.3L versus G200/1.9L is the valve cover; the 4ZD1 has a timing belt, with its own plastic cover mounted visibly in front of the cylinder head. The G200 has a timing chain, and it's not visible unless the valve cover is removed. I'm adding this because the VIN number says what it had when it left the factory, and may not be what's in there now, plus it's critical when getting parts.
You may already have one, but a good workshop manual is recommended. I use a Haynes #1641; some swear by them and others swear at them.
I replied to your PM for the radio, thanks for the info. I'm looking for an analog type; one that doesn't put a drain on the battery to keep the memory settings intact while the key is in my pocket. /R
Response to Goshua's intro: engine size
Response to Goshua's intro: engine size
'87 Isuzu p'up 4ZD1/2.3 gas, carb'd, 5spd, 4WD, base model, Fed spec